The arm of this study currently active is the preliminary evaluation of trimetrexate and leucovorin for the treatment of toxoplasma disease in immunocompromised patients. Folic acid metabolism is known to play an important role in key biosynthetic pathways in toxoplasma. As a potent dihydrofolate reductase inhibitor, trimetrexate is a logical therapeutic attempt to treat patients with toxoplasmosis who either cannot tolerate standard therapy with pyrimethamine and sulfadiazine or are resistant to that therapy. Initial presentation of the data was made at the 1989 AFCR National Meeting in May and a manuscript is in preparation. The importance of this work is that it assesses the role of monotherapy for treatment of toxoplasmosis and assesses a therapy for patients who cannot tolerate the standard regimen.